Safety strap buckles for automotive child safety seats are known, e.g. as described in European Patent Publication Number EP 0 867 131A1, comprising:                a buckle body connected to a first strap portion; and        a click-on lock mechanism housed inside the buckle body and designed to releasably lock two tongues connected to a second and third strap portion.        
In the embodiment described in the above patent application, the lock mechanism comprises a release button which is maintained, by a return spring, in an upper lock position in which the tongues are retained inside the buckle body by a rodlike retaining member engaging corresponding retaining seats defined by the two tongues.
The release button is movable, in a direction perpendicular to the insertion direction of the tongues and in opposition to the elastic force of the spring, into a lower release position, in which the retaining member is released from the seats on the tongues to permit expulsion of the tongues from the buckle body.
In the above known embodiment, the rodlike retaining member is supported by the release button, and so moves with the button between the two lock and release positions. As a result, when the tongues are inserted into the buckle body, thus moving the retaining member into the retaining seats, the release button is also moved with it and produces undesired noise.